Tries to cut peonies periodically put in black vehicle (8)

'put in black vehicle' is the definition.
(put in a hearse)

'tries to cut peonies periodically' is the wordplay.
'tries' becomes 'hears' (as in trying or hearing in a trial).
'to cut' is an insertion indicator.
'periodically' indicates alternate letters (letters must be selected 'every so often').
The alternating letters of 'peonies' are 'ene'.
'hears' going inside 'ene' is 'ENHEARSE'.